Struct positioned_io::Cursor

pub struct Cursor<I> { /* private fields */ }

Adapts a ReadAt or WriteAt into a Read or Write.

This wraps anything that read and write at offsets, turning into an object that can read or write at a file position. This allows you to use those types with all the many functions that expect a Read or Write.

Note that seeking on Cursor has limited functionality. We don’t know how many bytes are available, so we can’t use SeekFrom::End. See SizeCursor for another option.

Examples

use positioned_io::{ReadAt, Cursor};

struct NetworkStorage {
    // A remote disk that supports random access.
}

impl ReadAt for NetworkStorage {
    // ...
}

// Adapt our storage into a Read.
let storage = NetworkStorage::new(SOME_LOCATION);
let curs = Cursor::new_pos(storage, 1 << 30);

// Copy a segment to a file.
let mut input = curs.take(1 << 20);
let mut output = File::create("segment.out")?;
io::copy(&mut input, &mut output)?;

Implementations

impl<I> Cursor<I>

pub fn new_pos(io: I, pos: u64) -> Self

Create a new Cursor which starts reading at a specified offset.

Pass in a ReadAt or WriteAt as io.

pub fn new(io: I) -> Self

Create a new Cursor which starts reading at offset zero.

Pass in a ReadAt or WriteAt as io.

pub fn into_inner(self) -> I

Consume self and yield the inner ReadAt or WriteAt.

pub fn get_ref(&self) -> &I

Borrow the inner ReadAt or WriteAt.

pub fn get_mut(&mut self) -> &mut I

Borrow the inner ReadAt or WriteAt mutably.

pub fn position(&self) -> u64

Get the current read/write position.

pub fn set_position(&mut self, pos: u64)

Set the current read/write position.

Trait Implementations

impl<I: Clone> Clone for Cursor<I>

fn clone(&self) -> Cursor<I>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<I: Debug> Debug for Cursor<I>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<I: ReadAt> Read for Cursor<I>

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Read all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Read all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Read the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Read the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Selfwhere Self: Sized,

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

impl<I> Seek for Cursor<I>

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

🔬This is a nightly-only experimental API. (seek_seek_relative)

Seeks relative to the current position.

impl<I: WriteAt> Write for Cursor<I>

fn write(&mut self, buf: &[u8]) -> Result<usize>

Write a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Selfwhere Self: Sized,

Creates a “by reference” adapter for this instance of Write.